About Our Expertise

Members of the Climate Central staff and board are among the most respected leaders in climate science. Staff members are authorities in communicating climate and weather links, sea level rise, climate . . . . Read More

A 25-Year-Old Prediction of Water Scarcity in the Southwest Holds True, Study Finds

In 1986, environmental journalist Marc Reisner published Cadillac Desert: The American West and Its Disappearing Water, a landmark book surveying water use in the American Southwest. Having interviewed hundreds of people about the Southwest and learned the history of the region’s water infrastructure, Reisner concluded that more water was being pulled out of the West’s waterways than could be naturally replenished. He said the Southwest was due to run short on water, soon.

Nearly 25 years later, a group of researchers has put Reisner’s assertion to the test, checking to see if there is any scientific truth behind it. Armed with modern data from across the Southwest, the group, led by ecologist John Sabo from Arizona State University, found that many of Reisner’s claims were legitimate, and still hold true today.

“We asked, is it really as bad as [Reisner] said it is in the book, and are we still where we were in 1986?” explains Sabo, who assembled a group of experts to assess water, dams, fish, soil and crops across the Southwest using modern techniques. “Now we know the answer to both those questions: yes.” The findings from the new study have been published online in the Proceedings of the National Academy of Sciences (PNAS).

Revisiting the Cadillac Desert

Water levels in Lake Mead, pictured here in November 2008, reached a record low in October 2010. Credit: flickr/wenzday01.

In his book, Reisner claimed that humans were consuming most of the water from southwestern streams and rivers. The new review of watersheds shows that water users in the Southwest are already drawing on 76 percent of the available surface water to support more than 50 million people living in the region. Moreover, says Sabo, water usage could climb to as high as 86 percent if the population doubles in the Southwest.

Like all cities, those in the West and Southwest import water for people to use in their homes and businesses, as well as for industrial purposes. But this only accounts for a small portion of the total. Farming in arid states like California, Arizona, Colorado, and New Mexico requires a remarkably large amount of water compared to farms in eastern states. According to the study’s findings, it is this water-intensive agriculture that makes Los Angeles, Las Vegas and Phoenix the three largest water-consuming cities in the country.

After surveying the great western water reservoirs, such as Lake Mead and Lake Powell, Reisner also claimed that the build-up of sediments would eventually ruin the lakes for water storage and perhaps even electricity generation. The new study, however, found that sediment isn’t accumulating fast enough in these reservoirs to fill them completely in the next 100 years, although sediment has already reduced the ability of these lakes to deliver water to cities and farms.

Sabo and his collaborators also found that, true to Reisner’s original conclusions, the buildup of salt in the soil is particularly damaging to crops in the Southwest. Though salt accumulation is a potential threat to agriculture in many parts of the world, the study found that the Southwest is more vulnerable than other parts of the U.S.

Looking at a broader scale, the study estimates that farming revenue losses are ten times higher in the American West compared to the East — on the order of about $2.5 billion each year.

The already limited water resources in the Southwest have been further stressed over the past decade, during which a persistent drought has affected the region. In October 2010, Lake Mead in Nevada reached a record low level and is currently only about eight feet higher than the designated level of a critical water shortage. With the region so prone to drought, and potentially even more dry weather in the coming decades as the climate continues to change, Sabo says it’s important to find a way to cut back on the amount of water the Southwest is using. Many computer models project further drying in the Southwest as a consequence of global climate change.

“The message is that this is a regional problem,” says Sabo, “and that leaders from six U.S. states need to work together to make sure we keep more water running in the rivers.”

Reclaiming Sustainable Water in the Southwest

The original lesson from Cadillac Desert is familiar to southwesterners, who have heard warnings about water scarcity for years. These new findings lend further credibility to the idea that the region’s population is living beyond its water limits. But according to Peter Gleick, president of the Pacific Institute and a long time researcher of global water resources, identifying the problems in the Southwest hasn’t lead to the implementation of enough solutions over the past two decades. In a companion paper published in the same issue of PNAS, Gleick writes:

"Psychologically and socially, it is hard for millions of people who love this region to admit that it is fundamentally dry and that the rules for building, living, and working there must be different from those in the wet regions where most of these same people were born and raised."

Gleick says his research points to four strategies the Southwest should adopt to preserve enough water for the millions of people already living there.

“Firstly, we have to fundamentally rethink what we mean by water supplies,” he says. In the 20th century, dams and aqueducts were built to harness water in the rivers and transport it to cities. “But that isn’t going to be enough anymore. We’re already at the limits,” he says.

Gleick says it’s possible to tap water resources that are typically ignored, which could involve using treated wastewater or saltwater.

Seasonal drought outlook issued by the Climate Prediction Center, showing the development of drought conditions in much of the Southwest this winter. Credit: NOAA/Climate Prediction Center.

Next, he says the Southwest has to rethink its water demands and that water should be used more efficiently. “This doesn’t mean we will have to take shorter showers or brown the land around us,” he explains. “I mean doing everything we want to do, but with less water.” The trick, he says, is improving water efficiency everywhere it is affordable to do so, including improving irrigation systems for agriculture and switching to low flow faucets in homes.

Gleick says another important strategy is developing a more coordinated approach to managing water in the Southwest. Currently, different cities, counties and states control their own water with unique bylaws and regulations. “But in the Southwest watersheds define the landscape,” he says, “so, we should manage water at the regional level.” He recommends that different states and cities should work together as they develop policies for water usage.

Finally, Gleick says, “The important point is that we can’t look at the situation without climate change.” Because further climate change is inevitable, he says, so are the impacts on water availability around the world. “And it seems these changes will especially compound the problems in the Southwest rather than make them better.”

Already there are some authorities in the Southwest that are including climate change predictions in their water planning. For example, California’s Department of Water Resources released a five-year plan that calls for climate change considerations to be incorporated into all future water planning.

“The good news is, we are beginning to make these changes, in all areas,” says Gleick. People are rethinking water supply and demand, are cooperating more and are thinking about how climate change will affect water in the Southwest, he says.

On the other hand, Gleick warns, the water problems in the Southwest are bound to get worse in the coming years rather than better. “I’m not sure we’re moving fast enough to avoid more serious disruptions in the future.”